Calculation of Forest Potential Evapotranspiration of Okinawa in Japan Using the Penman Equation

Takuya Arakaki, Akira Shimizu, Naoki Kabeya, Hitoshi Ikuzawa, Takanori Shimizu, Shin’ichi Iida, Hiroshi Furugen

Forestry and Forest Products Research Institute, Tsukuba, Japan.
Incorporated Okinawa Prefecture Environment Science Centre, Urazoe, Japan.
Kyushu Research Centre, Forestry and Forest Products Research Institute, Kurokami, Japan.
Okinawa Prefecture Forest Resource Research Centre, Nago, Japan.

DOI: 10.4236/jwarp.2014.69077                

Abstract

The northern area of Okinawa Island is a unique forest area in Japan, with a distinctive ecosystem and subtropical climate. The area is a central region of forestry in Okinawa Prefecture. However, quantitative evaluation of the effects of the forest environment is inadequate. The authors began meteorological observation of this forested area to address this situation by setting up a weather station in 2009. In this study, we performed research on one of the major factors of the water cycle in forest ecosystems, evapotranspiration. We calculate seasonal changes in potential evapotranspiration through analysis of data from our weather station in 2013, because all measurement elements were assembled. To calculate potential evapotranspiration, we used the Penman equation. We found that the potential evapotranspiration in this forest area was 1170.5 mm in 2013. The mean temperature in 2013 was 20.7°C, yearly average relative humidity was 84.7%, and average wind speed was 1.40 m/s. Regarding the amount of evapotranspiration in the forests of northern Okinawa Island, which has not been previously obtained, it has become possible to calculate the amount of potential evapotranspiration using the Penman equation.

Keywords

Potential Evapotranspiration, Penman Equation, Weather Station, Subtropical Region, Evergreen Forest

Conflicts of Interest

The authors declare no conflicts of interest.

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